This application is based upon and claims priority from prior French Patent Application No. 9808561, filed Jul. 3, 1998, the entire disclosure of which is herein incorporated by reference.
The present invention generally relates to semiconductor electronics and more specifically, a machine for testing electronic components or chips which make up integrated circuits produced in a wafer and each including multiplicity of electrical connection pads formed on the surface of the wafer.
Known test machines generally include a test head which has a multiplicity of electrical connection test prods and means, and in general, a manipulator, for moving the wafer to be tested with respect to the head so as to bring the ends of the prods into contact with the pads of each chip, in succession.
Such machines are used for testing electronic components or chips which make up integrated circuits produced in a wafer and each including a multiplicity of electrical connection pads formed on the surface of the wafer.
When the end of each prod comes into contact with each of pads of a chip to be tested, the prods, which do not extend perpendicularly to the wafer, deform slightly in order to produce a contact force and their ends slide over the surface of the pads, this sliding action improving the electrical connection by scraping off the oxides.
In order to improve the results of the tests carried out, the electronic chips are placed in situations similar to those in which they will be in during their subsequent use. This is why some manipulators are provided, in their test zone, with heating means which allow the wafers to be tested to be heated from below up to temperatures which may range between 80xc2x0 C. and 125xc2x0 C. In practice, when a wafer, to be tested, is brought into the test zone, and after it has reached the desired temperature, its electronic chips are tested in succession.
Especially given the fact that the wafers undergo dimensional variations when they are heated, that the heated wafer radiates heat in an uncontrolled manner towards the test head and, in particular, towards its electrical connection test prods, that the electrical connection test prods take heat from the heated wafer when they are in contact with its surface and that each side of the connection pads of the electronic chips is generally less than 100 microns, great difficulties are encountered at the present time in controlling the space around the electrical connection test prods of the test head and in programming the horizontal displacement steps of the manipulator which allow it to pass from one electronic chip to another.
Further, when an electronic chip is declared to be defective, it may not be known for certain whether this result is actually due to the electronic chip tested. This negative result may in fact be due to the lack of contact between at least one of the electrical connection test prods and the corresponding pad on the electronic chip tested.